Upgrade Your Castle
One option you may pass over in Fire Emblem Heroes is the ability to upgrade your castle, and receive various benefits by doing so. Each level you upgrade your castle, you’ll get a bonus to the experience your characters earn in battle. You will need to use orbs to upgrade it, however.
When you’re on the home screen, look at the top left corner and you’ll see a small green button with a house on it, this is the upgrade button. Simply click on it and a window will come up with upgrade options. Alternatively, you can go to the Shop tab and select castle upgrade there. On top of everything, your castle will even get a shiny new coat of paint.
Of course, you will want to budget your orbs as you also need them to summon new heroes, but make sure to occasionally pop in and purchase an upgrade or two.
